Electronic driver for water treatment system UV bulb

ABSTRACT

A driver or ballast for the ultraviolet bulb of a water treatment system. The driver includes a step-up transformer and a feedback oscillator connected between the secondary and the primary of the transformer. The secondary of the transformer also is selectably connected through one of two different capacitor compensators depending on water flow through the system. In a low intensity mode, the current and the power factor output of the driver are relatively low--preferably just enough to keep the bulb filaments energized. In a high intensity mode, the current and the power factor are relatively high to power the bulb at a relatively high efficiency. The driver operates at a relatively low DC voltage. A voltage converter selected as function of the local line voltage converts the AC line voltage to the necessary DC voltage.

BACKGROUND OF THE INVENTION

The present invention relates to water treatment systems, and moreparticularly to an electronic driver or ballast for an ultraviolethousehold water treatment system.

Household water treatment systems have gained widespread popularity,particularly in areas with less-than-ideal potable water. A householdsystem or unit is mounted on a single tap to selectively treat waterflowing through the tap. Treatment may include filtration, irradiation,or both. The most effective water treatment systems include ultraviolet(UV) irradiation to sterilize the water stream. It is well known thatsuch UV treatment kills bacteria and viruses with an extremely highdegree of reliability. The water to be treated is routed through acontainer, and a UV light source within or adjacent to the containerdirects UV light through the water stream.

A first issue with UV water treatment systems relates to intensitycontrol of the UV bulb. At least three factors are considered indetermining the intensity of the UV light. First, it is desirable tooperate the bulb at a relatively high intensity to achieve the maximum"kill rate" when water is flowing. Second, it is desirable to neverextinguish the bulb, for example as one might be tempted to do whenwater flow stops, because of the start-up lag in bringing the UVintensity back up to treatment intensity when water flow is detected.Third, it is desirable to reduce bulb wattage or power when water flowstops to avoid excessive warming of the water "stagnated" within thetreatment chamber.

Prior artisans have accommodated these considerations by designing bulbintensity control circuits capable of selectively driving the bulb atrelatively high and low intensities. One such circuit is illustrated inU.S. Pat. No. 5,324,423 issued Jun. 28, 1994, to Markham and entitled UVBULB INTENSITY CONTROL FOR WATER TREATMENT SYSTEM. When water isflowing, as detected by a flow switch, the bulb is operated at highintensity to achieve the desired kill rate. When water flow stops, thebulb is operated at a lower intensity to avoid excessive warming of thewater and to prevent extinguishing of the bulb. While the Markhamcircuit is a significant advance in the art, it is not without itsdrawbacks. The inductive ballast is more expensive and less efficientthan desired. Further, the ballast is relatively heavy and noisy.

A second issue with water treatment systems is the possibility ofelectrical shock to a user. While the risk is low, the consequences canbe serious because the systems plug directly into the household linevoltage, which is 110 volts in the United States and varies from 100volts to 264 volts throughout the world.

A third issue with water treatment systems is the variance in designfrom country to country. As noted in the preceding paragraph, linevoltage can vary from 100 volts to 264 volts. Additionally, linefrequency varies from 50 Hz to 60 Hz. Consequently, the electronicspackage of a water treatment system must be custom tailored to the linevoltage/frequency combination for that country. This leads to design,manufacture, and inventory problems.

SUMMARY OF THE INVENTION

The aforementioned problems are overcome in the present inventionproviding a UV water treatment system having improved intensity controland a uniform electrical/electronics design.

In a first aspect of the invention, an electronic driver, rather than aninductive ballast, operates the ultraviolet bulb at two distinctintensities depending on water flow. More specifically, the controlcircuit includes a step-up transformer having a primary and secondary. Afeedback oscillator is connected between the secondary and the primary.Additionally, the secondary goes through one of two capacitancesdepending on water flow. When water flow is not detected, the lowercapacitance is electrically connected to provide reduced current andpower factor to the bulb. When water flow is detected, the highercapacitance is electrically connected to drive the bulb at fullintensity.

The advantages of the first aspect are numerous. First, the bulbfilaments remain excited even in the low intensity mode, permittingrapid reintensification upon the detection of water flow. Second,switching from low intensity to high intensity is virtuallyinstantaneous. Third, the cost is lower than prior art circuits. Fourth,the operation is more efficient. Fifth, the relatively heavy and noisyinductive ballast of the prior art is eliminated.

In a second aspect of the invention, the bulb control circuit isdesigned to be powered by a low, standard, DC voltage, which in thepreferred embodiment is 12 volts. A DC voltage converter unique to theapplicable line voltage/frequency combination is provided to convertlocal line AC voltage to the standard DC voltage.

The advantages of this second aspect also are numerous. First, theelectronics package within the water treatment system can remain thesame regardless of the line voltage/frequency. Only the DC voltageconverter is different depending on the line voltage/frequency. Second,and consequently, design is standardized; manufacture is standardized;and inventories are reduced. Third, the risk of serious electrical shockis vastly reduced. Fourth, local electrical code approval is requiredonly for the voltage converter and not for the treatment system itself.

These and other objects, advantages, and features of the invention willbe more readily understood and appreciated by reference to the detaileddescription of the preferred embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a water treatment system in which the UVelectronic driver of the present invention may be used;

FIG. 2 is a schematic circuit diagram of the electronic driver; and

FIG. 3 is a schematic illustration of the physical components of thewater treatment system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The ultraviolet (UV) electronic driver of the present invention isillustrated in FIG. 2 and generally designated 10. The system includes apower conditioning circuit 12; a step-up transformer including a core13, a primary circuit 14a, and a secondary 14b; a feedback oscillator16; a capacitance circuit 18; and a voltage monitor 20. The controlcircuit 10 is connected to the UV bulb 22 to drive the bulb at twoseparate intensities. The bulb is driven at a relatively low intensitywhen water flow has stopped to prevent undesirable temperature rise inthe stagnated water. The bulb 22 is driven at a relatively highintensity when water flow is detected to provide maximum kill rate.

Turning to FIG. 1, the electronic driver 10 is included in a watertreatment system of the type schematically illustrated in FIG. 1 andgenerally designated 30. The line connections illustrated between andwithin the blocks 30, 32, and 36 are fluid connections permitting waterflow through the treatment system 30. Generally speaking, the watertreatment system is connected to a potable water supply 32 and includesa valve 34 for selectively routing water either directly to the tapdischarge 36 or to the filter and sterilization units 38 and 40. Thevalve may be of the type illustrated in U.S. Pat. No. 5,279,329 issuedJan. 18, 1994, to Pippel and entitled FAUCET DIVERTER VALVE.

In the water treatment system 30, the water can be sent directly to thetap discharge 36 by putting the valve 34 in a first manually selectedposition. Alternatively, the valve can be placed in a second manuallyselected position where the water is routed sequentially through thefilter 38 and the sterilization unit 40 before being discharged from thetap at 36. The tap can include two discharges-one for treated water anda second for untreated water. The filter 38 is preferably acarbon-activated filter. The UV sterilization unit includes a waterchamber, container, or passageway in conjunction with the ultraviolet(I/V) source of light 22 for sterilizing water flowing therethrough.Treatment systems of the type illustrated in FIG. 1 are generally wellknown to those having ordinary skill in the art.

The UV unit 40 within the treatment system 30 receives power from thevoltage converter 41. The voltage converter is of conventional designand construction generally well known to those skilled in the art. Theparticulars of the converter will depend on the voltage and frequency ofthe AC line voltage. The converter is selected to convert the AC linevoltage to 12 volts DC to power the UV unit 40. This design andconstruction (1) permits the electronics package within the system toremain the same, with only the converter changing from locale to localedepending on the line voltage; (2) reduces the risk of seriouselectrical shock to the user; (3) requires local electrical codeapproval typically only for the converter; (4) reduces inventory; and(5) accommodates possible future battery back-up.

The FIG. 1 components also are schematically physically illustrated inFIG. 3. The housing 110 is a counter-top item that encloses the filter38 and the UV unit 40 illustrated in FIG. 1. The valve 34 is connectedto the tap or other water supply 32 and also is connected to the housingby hoses or lines 112 and 114. Water W is shown exiting the discharge36. The voltage converter 41 is plugged into a line voltage electricaloutlet 116. A power line 118 delivers the 12-volt DC power to systemelectronics. A plug 120 on line 118 connects to the housing 110.

Returning to FIG. 2, the power conditioning circuit 12 is generallyconventional and is selected to interface the driver 10 with a 12-voltDC power supply, such as the voltage converter 41. More specifically,the lines 42 and 43 connect to the 12-volt supply 44 and the ground 46,respectively. The signal conditioning circuit 12 includes a diode50/capacitor 52 pair connected between the 12-volt source and ground.The conditioned 12-volt voltage is denominated 55 and is supplied toother components, for example, a main circuit board (not shown) in thecontrol 90 via lines 51 and 53. A diode 48 is located in the line 51.Diodes 48 and 50 prevent damage to the circuit in the case of anaccidental reverse power connection.

Additionally, a positive temperature coefficient (PTC) resistor 54 isincluded to protect the circuit 10 from excessive power dissipation. Asthe bulb 22 ages, the voltage required to maintain the plasma-columnacross the filaments 23 alive or active increases. This increasedvoltage requirement draws more current from the power supply 44 andconsequently through the PTC resistor 54. The PTC resistor opens up whenthe current draw exceeds a design parameter so as to protect the powersupply 44 and the circuit 10.

The step-up transformer includes the core 13, the primary 14a, and thesecondaries 14b and 14b'. The primary 14a includes two taps 60 and 62.The primary 14a is center tapped between taps 60 and 62, and the 12-voltsource 55 is connected through the inductor 56 to the center tap 58.Capacitor 63 is electrically connected between the taps 60 and 62. Thesecondary 14b includes taps 64, 65, 66, 67, and 68. A portion of thesecondary denominated 14b' is illustrated within the oscillator circuit16 and includes taps 69 and 70.

The oscillator circuit 16 is electrically connected between thesecondary 14b' and the primary 14a. A pair of resistors 74 and 76 areconnected in series across the taps 69 and 70. A resistor 78electrically connects both resistors 74 and 76 to ground 46. A pair oftransistors 79 and 80 have bases electrically connected to the resistors74 and 76, respectively. The collector of transistor 79 is electricallyconnected to tap 60, and the collector of transistor 80 is electricallyconnected to the tap 62. The emitters of the transistors 79 and 80 areelectrically connected together to ground 46. Capacitor 64 and/orresistors 74 and 76 can be adjusted to change the oscillator frequency.

The oscillator 16 is a feedback oscillator of push/pull design. Thetransformer provides inductive feedback. The voltage across thesecondary 14b' between taps 69 and 70 is used to drive the primary 14a.In the preferred embodiment, the oscillator drives the primary at afrequency of 23,200 Hz in the high-intensity mode and 35,700 Hz in thelow-intensity mode. Preferably the frequencies are selected to optimizethe efficiency of the bulb 22, and the frequencies will vary dependingon the application. In the high mode, both the current and the powerfactor are relatively high. In the low mode, both the current and thepower factor are relatively low-preferably just enough to keep theplasma arc column between the filaments 23 energized. The current can beeasily adjusted by changing either or both of the capacitors 96 (highmode) and 98 (low mode).

A transistor 81 is electrically connected in series between the tap 69and the ground 46. The base of the transistor 81 receives unconditionedvoltage through resistors 71 and 72. When the system is operatingnormally, the transistor 81 is nonconductive and therefore does notimpact the oscillator 16. A magnetic reed switch 82 is electricallyconnected in series between the ground 46 and the junction of theresistors 71 and 72. The switch 82 is mounted in the water treatmentsystem 30 as is generally known so that it is closed when the bulb 22 isphysically shrouded and open when the bulb is not shrouded. For example,the switch typically is mounted to be actuated by the physical presenceor absence of a shroud or cover over the bulb 22. If the switch 82 isopen, indicating that the shroud is not present, voltage is supplied tothe base of the transistor 81; and consequently the transistor groundsthe base of the oscillator transistor 81 in the circuit 16. This resultsin the bulb not being lit. This feature prevents human eyes from beingdamaged by inadvertent UV irradiation.

Although a feedback transformer oscillator with capacitor compensationhas been described, it will be readily appreciated that many otheroscillators could be used. Suitable alternatives include feedbacktransformer oscillators, feedback amplifier oscillators, and oscillatorsimplemented using integrated circuits (e.g. a 555 timer), transistors,crystals, or ceramic resonators.

The voltage monitor circuit 20 is illustrated and described inco-pending application Ser. No. 002,820 filed Jan. 11, 1993, by Markhamand entitled WATER TREATMENT SYSTEM ULTRAVIOLET VOLTAGE MONITOR CIRCUIT.Suffice it to say that the monitor circuit 20 provides output signals onlines 84 and 86 indicating if the bulb is out, the ballast is out, orboth are functioning properly. The signals can be used by the control 90to illuminate indicator lights, sound alarms, or otherwise provideinformation to the user.

The control 90 is connected to a flow switch 92. The flow switch can beone of any number generally known in the art. The flow switch of thepresent invention simply indicates whether water is flowing or not.Other flow switches indicating the relative volume of flow may be used.

The capacitance circuit 18 is connected to the control 90 via line 94.The capacitance circuit includes a capacitor 96 of relatively highcapacitance, a capacitor 98 of relatively low capacitance, and asolenoid switch 100 powered by the conditioned voltage. Both of thecapacitors 96 and 98 are electrically connected between the tap 66 andthe solenoid 100. Depending upon the position of the relay, thecapacitors 96 and 98 are connected between the secondary 14b and thebulb 22. Other capacitor circuits providing different capacitances maybe substituted.

The bulb 22 is conventional in the art and includes a pair of filaments23a and 23b. The filament 23a is electrically connected to the secondarytaps 64 and 65; and the filament 23b is electrically connected to thesecondary taps 67 and 68. Capacitors 102 and 104 are included within theconnections. The described connections keep the filaments heated andexcited and therefore in a condition to more rapidly supply theelectrons needed in the high-intensity state when the driver switches tothe high intensity mode.

Operation

The default position of the relay 100 is as illustrated in FIG. 2 sothat the capacitor 96 is electrically connected between the secondary 66and the bulb 22. The high capacitance of capacitor 96 operates the bulb22 in the high-intensity mode. This mode is selected as the defaultposition to insure irradiation of all water-both flowing andstagnant--even upon failure of the control 90 or the switch 92.

A fixed time after no water flow is detected by the switch 92, thecontrol 90 sinks voltage through the line 94, which activates thesolenoid 100. This causes the solenoid be activated to its unnaturalstate (low mode), disconnecting capacitor 96 and connecting capacitor 98between the secondary 14b and the bulb 22. The relatively lowcapacitance operates the bulb at a greatly reduced intensity and power.

The present invention therefore provides an effective, simple,inexpensive circuit for controlling bulb intensity and power withoutsacrificing bulb life. The electronic driver also eliminates the needfor a relatively heavy and noisy inductive ballast and a relativelyunreliable starter.

The above description is that of a preferred embodiment of theinvention. Various alternations and changes can be made withoutdeparting from the spirit and broader aspects of the invention as setforth in the appended claims, which are to be interpreted in accordancewith the principals of patent law including the doctrine of equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A driver system for anultraviolet bulb in a water treatment system comprising: a flow switchoperative for detecting fluid flow,a step-up transformer including aprimary and a secondary; an oscillator operative for controlling theelectrical power supplied to said primary of said transformer; and anoscillator control means responsive to the flow switch for controllingthe frequency at which said oscillator operates, said oscillator controlmeans driving said oscillator at a first frequency when water is notflowing and at a second frequency when water is flowing.
 2. A driversystem for an ultraviolet bulb in a water treatment system comprising:aflow switch operative for detecting fluid flow, a step-up transformerincluding a primary and a secondary; an oscillator operative forcontrolling the electrical power supplied to said primary of saidtransformer, said oscillator comprising a feedback oscillatorelectrically connected between said secondary and said primary of saidtransformer; and an oscillator control means responsive to the flowswitch for controlling the frequency at which said oscillator operates,said oscillator control means driving said oscillator at a firstfrequency when water is not flowing and at a second frequency when wateris flowing, said oscillator control means comprising variablecapacitance compensation means electrically connected between saidsecondary of said transformer and the bulb, said compensation meansbeing responsive to the flow switch for providing a first capacitancecompensation to the bulb when water is not flowing and for providing asecond capacitance compensation to the bulb when water is flowing.
 3. Adriver as defined in claim 2 wherein said compensation means includes apair of capacitors and switch means responsive to the flow switch forselectably connecting one of said capacitors to said secondary.
 4. Adriver as defined in claim 2 wherein said transformer is a center-taptransformer.
 5. A water treatment system comprising:an ultraviolet bulb;water flow switch means for providing a signal indicative of whetherwater is flowing through said system; a transformer having a primaryadapted to be electrically connected to a power supply and a secondaryelectrically connected to said bulb; an oscillator electricallyconnected to said transformer primary; and a control means forcontrolling the frequency at which said oscillator operates, saidcontrol means operating said oscillator at a first frequency when saidwater flow switch means signal indicates that water is not flowing, saidcontrol means operating said oscillator at a second frequency when saidwater flow switch means signal indicates that water is flowing.
 6. Awater treatment system comprising:an ultraviolet bulb; water flow switchmeans for providing a signal indicative of whether water is flowingthrough said system; a transformer having a primary and a secondaryelectrically connected to said bulb; an oscillator electricallyconnected to said transformer primary, said oscillator comprising afeedback oscillator electrically connected between said transformersecondary and said transformer primary; and a control means forcontrolling the frequency at which said oscillator operates, saidcontrol means operating said oscillator at a first frequency when saidwater flow switch means signal indicates that water is not flowing, saidcontrol means operating said oscillator at a second frequency when saidwater flow switch means signal indicates that water is flowing, saidcontrol means including a pair of compensators having first and secondcapacitances said control means further including compensator switchmeans for selectably electrically connecting one of said compensatorsbetween said transformer secondary and said bulb, said compensatorswitch means connecting said first compensator to said secondary whensaid water flow switch means signal indicates that water is not flowing,said compensator switch means connecting said second compensator to saidsecondary when said water flow switch means signal indicates that wateris flowing.
 7. A water treatment system as defined in claim 6 whereineach of said compensators comprises a capacitor.
 8. A water treatmentsystem as defined in claim 6 wherein said transformer comprises acenter-tap transformer.
 9. An electrical ballast system for a watertreatment system having an ultraviolet bulb comprising:a water flowindicator means for indicating water flow through said system; atransformer having a primary and a secondary adapted to be connected tothe bulb; a feedback oscillator connected between said transformerprimary and said transformer secondary; and variable capacitancecompensator means connected to said transformer secondary for providinga selectable capacitance compensation to the bulb responsive to thewater flow indicator means.
 10. An electrical ballast as defined inclaim 9 wherein said compensator means includes a pair of capacitorshaving relatively high and low capacitances and switch means forselectably connecting one of said capacitors between said transformersecondary and the bulb.
 11. An electrical ballast as defined in claim 9wherein said transformer comprises a center-tap transformer.